Heat transport device

ABSTRACT

A heat transport device ( 1 A) is provided with: a circulation path unit ( 10 ) in which a heat recovery unit ( 11 ) that vaporizing a heat transport medium and a condensation unit ( 12 ) that condenses the heat transport medium vaporized in the heat recovery unit ( 11 ) are incorporated, and which has a vacuum state; a branch path unit ( 20 ) which branches from the circulation path unit ( 10 ), and in which a valve ( 22 ) capable of controlling flow is incorporated; and an ECU ( 40 A) which implements a first control unit and is configured to, when it is recognized that there is an increase in the pressure within the circulation path unit ( 10 ) under the same operating condition, open and close the valve ( 22 ) in the state in which the pressure within the circulation path unit ( 10 ) is higher than a predetermined pressure (α).

TECHNICAL FIELD

The present invention relates to heat transport devices.

BACKGROUND ART

As a heat transport device, there is known a vapor loop structure inwhich a heat transport medium circulates naturally while a sequence ofreceiving heat in a condensed state and radiating heat in a vaporizedstate is repeatedly carried out. In this regard, an engine waste heatutilization device that utilizes waste heat of an engine is disclosed inPatent Document 1 as an art of recovering and utilizing heat by such avapor loop structure.

Besides, arts that are considered as being relative to the presentinvention are disclosed in Patent Documents 2 through 5. In PatentDocument 2, there is disclosed a waste heat recovery device in which,when an engine provided with a Rankine cycle is stopped, negativepressure in a system due to condensation of vapor in cooling is reducedand breakage of a pipe or the like is avoided. In Patent Document 3,disclosed is an internal combustion engine provided with a heat recoverydevice in which a coolant vapor in an engine cooling system is heated byengine exhaust and a turbine is thus driven. In paragraph 0037 of thespecification of Patent Document 3, there is a disclosure that theinside of a cooling path is evacuated when the engine is stopped and airmay be sucked therein from the outside and that a vacuum pump isprovided to remove air in the cooling path.

In Patent Document 4, there is disclosed a warm-up apparatus forinternal combustion engines provided with a waste heat recovery devicehaving a loop type heat pipe structure, which is a kind of the vaporloop structure. In paragraph 0055 of the specification of PatentDocument 4, there is a disclosure that the inside of the waste heatrecovery device of the loop type heat pipe structure is set in thevacuum state. In Patent Document 5, disclosed is a vehicle coolingapparatus capable of venting air from a cooling water path.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Patent Application Publication No.2010-156315

Patent Document 2: Japanese Patent Application Publication No.2008-185001

Patent Document 3: Japanese Patent Application Publication No.2000-345835

Patent Document 4: Japanese Patent Application Publication No.2010-281236

Patent Document 5: Japanese Patent Application Publication No.2008-121434

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

In the heat transport device, there is a possibility that air is suckedin a circulation path unit in the vacuum state from the outside. If theair suction takes place, air exists instead of heat transport medium andthe amount of receiving heat and the amount of radiating heat decreasecorrespondingly, so that the device performance may deteriorate.

In this regard, specifically, there is an exemplary heat transportdevice equipped with the above-described vapor loop structure. In thisheat transport device, the heat transport medium is vaporized in a heatrecovery unit that receives heat and moves diffusely to finally reach acondensation unit that radiates heat. Thus, if the air suction takesplace in the heat transport device, the movement of the heat transportmedium is impeded greatly. Thus, heat is not transported at all or theheat transport performance deteriorates considerably, so that the deviceperformance may deteriorate greatly.

It can be said that the air suction is not concerned particularly if theinside of the circulation path unit is hermetically sealed for example.However, it is difficult to hermetically seal the inside of thecirculation path unit and is not always realistic. Therefore, it isgenerally conceivable that various types of seal members, for example,are used to improve the hermetic seal of the inside of the circulationpath unit. However, in this case, there is a possibility that more orless air suction takes place and air may be gradually accumulated in thecirculation path unit. Further, in that case, the seal member has agedeterioration, which makes it difficult to maintain the highly hermeticseal for a long time and to thus suppress the air suction itself.

For the above reasons, a realistic way to cope with the deviceperformance deterioration should be considered on the assumption thatthe air suction takes place. For this purpose, as disclosed in PatentDocument 3, for example, it is conceivable that the vacuum pump is usedto remove air from the circulation path unit. However, this case may bedisadvantageous in terms of cost and downsizing, for example.

The present invention aims to provide a heat transport device that hasan advantageous structure in terms of, for example, cost and is capableof recovering the device performance that deteriorates due to airsuction.

Means for Solving the Problems

The present invention is a heat transport device comprising: acirculation path unit in which a heat recovery unit that vaporizing aheat transport medium and a condensation unit that condenses the heattransport medium vaporized in the heat recovery unit are incorporated,and which has a vacuum state; a branch path unit which branches from thecirculation path unit, and in which a valve capable of controlling flowis incorporated; and a first control unit configured to open and closethe valve in a state in which pressure in the circulation path unit ishigher than a predetermined pressure when it is detected or estimatedthat the circulation path unit sucks air.

The present invention may be configured so that the heat transportdevice further comprises a reserve tank that stores, in a liquid phase,heat transport medium with which the circulation path unit is to bereplenished, the branch path unit being connected to the reserve tank soas to have an opening located in a position lower than a height of aliquid level that is to be at least ensured in the serve tank; andwherein the heat transport device further comprises a replenishmentquantity calculation unit that calculates a quantity of heat transportmedium with which the circulation path unit should be replenished fromthe reserve tank, and a second control unit configured to open and closethe valve in accordance with the quantity of heat transport mediumcalculated by the replenishment quantity calculation unit in a state inwhich the pressure in the circulation path unit is lower than thepredetermined pressure after the first control unit opens and closes thevalve.

The present invention may be configured to further comprise a freezingdetermination unit that determines whether the heat transport mediumcirculating in the circulation path unit has a possibility of freezing;and a reduction-in-quantity correction unit that performs areduction-in-quantity correction in which the quantity of heat transportmedium is reduced when an operation start condition is met from anoperation stop state if the freezing determination unit determines thatthe heat transport medium that circulates in the circulation path unithas a possibility of freezing.

The present invention may be configured so that wherein the heattransport medium naturally circulates in the circulation path unit whilea sequence of receiving heat in a condensed state in the heat recoveryunit and radiating heat in a vaporized state in the condensation unit isrepeatedly carried out.

The present invention may be configured so that the heat transport unitis mounted in a vehicle with an internal combustion engine, and the heatrecovery unit recovers exhaust heat of the internal combustion engine.

Effects of the Invention

According to the present invention, it is possible to recover the deviceperformance that deteriorates due to air suction with an advantageousstructure in terms of cost, for example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a schematic structure of a heat transport device;

FIG. 2 is a flowchart of an exemplary control in accordance with a firstembodiment;

FIG. 3 is a flowchart of an exemplary control in accordance with asecond embodiment;

FIG. 4 is a flowchart of an exemplary control in accordance with a thirdembodiment;

FIG. 5 is a flowchart of an exemplary control in accordance with a fifthembodiment; and

FIG. 6 is a flowchart of an exemplary control in accordance with a sixthembodiment.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

A description will now be given of embodiments for carrying out theinvention with reference to the accompanying drawings.

First Embodiment

FIG. 1 is a diagram of a schematic structure of a heat transport device1A. In FIG. 1, there are illustrated, together with the heat transportdevice 1A, an internal combustion engine 50, an exhaust pipe 51, astarter converter 52 and an underfloor converter 53. The structuralparts illustrated in FIG. 1 are mounted in a vehicle. The heat transportdevice 1A is provided with a circulation path unit 10, a branch pathunit 20, a reserve tank 30, and an ECU 40A. The heat transport device 1Acarries out a heat transport with a heat transport medium utilizing aphenomenon such that vaporization occurs due to heat reception andcondensation occurs due to heat radiation (hereinafter referred tosimply as transport medium).

The circulation path unit 10 is provided with a heat recovery unit 11, acondensation unit 12, a feed pipe 13, and a return pipe 14. Thecirculation path unit 10 with those structural parts forms a circulationpath in which the heat recovery unit 11 and the condensation unit 12 areincorporated. The circulation path unit 10 is beforehand filled with thetransport medium in a depressurized state below the atmospheric pressure(for example, −100 kPa). By this, the boiling point of the transportmedium is adjusted to match the operating environment in the heattransport by the transport medium. In this regard, specifically, thetransport medium is H₂O in the present embodiment.

The heat recovery unit 11 is a heat exchanger and vaporizes thetransport medium. In the present embodiment, the heat recovery unit 11is specifically a heat exchanger that performs a heat exchange betweenthe exhaust of the internal combustion engine 50 and the transportmedium and thus recovers heat from the exhaust to vaporize the transportmedium. In this regard, the start of the internal combustion engine 50is a condition for starting the operation of the heat transport device1A, and the stop of the internal combustion engine 50 is a condition forstopping the operation of the heat transport device 1A. The coolingprogresses after the condition for stopping the operation is met andthus the condensation of the transport medium progresses, whereby thecirculation path unit 10 has the vacuum state.

The exhaust of the internal combustion engine 50 is cleaned by thestarter converter 52 and the underfloor converter 53 provided in theexhaust pipe 51, and is expelled from the exhaust pipe 51. The heatrecovery unit 11 is provided specifically in a part of the exhaust pipe51 that is downstream from the underfloor converter 53.

The condensation unit 12 is a unit in which vapor, which is thevaporized transport medium, is condensed, and utilizes heat transportedby vapor. In the present embodiment, specifically, the condensation unit12 is a part of the internal combustion engine 50 that utilizes heattransported by the vapor for warming up. Thus, the heat transport device1A is provided with the condensation unit 12 so as to be shared with theinternal combustion engine 50. The condensation unit 12 may be aspecific part of the internal combustion engine 50 capable of reducing,by heat transported by the vapor, the friction torque of the internalcombustion engine 50 during cold conditions. Specifically, thecondensation unit 12 may be a bearing unit that supports a crankshaft ofthe internal combustion engine 50.

The feed pipe 13 feeds vapor to the condensation unit 12 from the heatrecovery unit 11. The feed pipe 13 is provided with a pressure sensor 61and a temperature sensor 62. The pressure sensor 61 senses pressure inthe circulation path unit 10 by sensing pressure in the feed pipe 13(hereinafter referred to as system internal pressure). The temperaturesensor 62 senses the temperature in the circulation path unit 10 bysensing the temperature in the feed pipe 13 (hereinafter referred to assystem internal temperatures).

In this regard, the pressure sensor 61 is provided in a part of thecirculation path unit 10 having the highest position. The temperaturesensor 62 is provided so as to sense the temperature of the part of thecirculation path unit 10 in which the pressure sensor 61 senses thesystem internal pressure. The return pipe 14 returns the condensedtransport medium to the heat recovery unit 11 from the condensation unit12. Specifically, the return pipe 14 is provided so as to return thecondensed transport medium to the heat recovery unit 11 from thecondensation unit 12 due to the function of gravity together with theheat recovery unit 11.

The branch path unit 20 is provided with a branch pipe 21 and a valve22. The branch path unit 20 with the above structural parts forms abranch path in which the valve 22 is incorporated. The branch pipe 21branches from the circulation path unit 10. The valve 22 controls theflow in the branch pipe 21. Specifically, the valve 22 is a flow-rateadjustment valve. The valve 22 may be an open/close valve, for example.The branch pipe 21 is connected to the reserve tank 30 via the valve 22.The reserve tank 30 stores, in the liquid phase, the transport mediumwith which the circulation path unit 10 is replenished.

In this regard, specifically, the branch pipe 21 is connected to abottom portion of the reserve tank 30 via the valve 22 from beneath it.The branch pipe 21 has an opening located in a position lower than aheight of the liquid level that is to be at least ensured in the reservetank 30. More specifically, the branch pipe 21 connected to the reservetank 30 is provided as follows. That is, the branch pipe 21 is providedso as to branch and extend from the return pipe 14 upwards in thedirection of gravity. The branch pipe 21 is provided so as to branchfrom a part of the return pipe 14 closer to the heat recovery unit 11.

The reserve tank 30 is specifically a type of tank that is open to theatmosphere in which atmospheric pressure is exerted on the transportmedium stored in the liquid phase. The reserve tank 30 has a capacitythat enables the transport medium circulating in the circulation pathunit 10 to be stored in the liquid phase in addition to the transportmedium stored in the liquid phase. For example, the reserve tank 30 maybe a tank with a breather valve that opens with a given pressure andthus suppresses increase in the internal pressure.

The ECU 40A is an electronic control device, to which electricallyconnected are sensors and switches including the pressure sensor 61, thetemperature sensor 62, an atmospheric pressure sensor 63 that sensesatmospheric pressure, an atmospheric temperature sensor 64 that sensesatmospheric temperature, and a group of sensors 65. The valve 22 iselectrically connected as a control object.

The sensor group 65 includes a crank angle sensor capable of detectingan engine speed NE of the internal combustion engine 50, an airflowmeter capable of measuring the quantity of intake air of the internalcombustion engine 50, an acceleration position sensor that senses thedegree of depression of an accelerator pedal, which makes a request theinternal combustion engine 50 for acceleration, a water temperaturesensor that senses the temperature of cooling water of the internalcombustion engine 50, an exhaust temperature sensor that senses thetemperature of exhaust of the internal combustion engine 50, and anignition switch for starting up the internal combustion engine 50. Theoutputs of the sensor group 65 and a variety of information based on theoutputs of the sensor group 65 may be acquired by an ECU for controllingthe internal combustion engine 50, for example. The ECU 40A may be anECU for controlling the internal combustion engine 50.

In the ECU 40A, a CPU performs a process in accordance with a programstored in a ROM while using a temporary memory area in a RAM asnecessary. This implements various functional parts such as a firstcontrol unit described below.

A first control unit opens and closes the valve 22 in a state in whichthe system internal pressure is higher than a predetermined pressure αin a case where it is recognized that there is an increase in the systeminternal pressure in the circulation path unit 10 under the sameoperating conditions. The operating conditions are, for example, thequantity of the transport medium in the circulation path unit 10, theatmospheric temperature, the thermal state of the heat recovery unit 11,and the thermal state of the condensation unit 12. Specifically, thecase where it is recognized that there is an increase in the systeminternal pressure in the circulation path unit 10 under the sameoperating conditions is a case where it is detected or estimated thatthe circulation path part 10 sucks air. That is, in this case, under thesame operating conditions, the system internal pressure increases due toair suction, as compared with a case where no air is sucked.

Thus, the ECU further implements a suction determination unit thatdetermines whether the circulation path unit 10 has sucked air.Therefore, specifically, if the suction determination unit determinesthat the circulation path unit 10 has sucked air, the first control unitopens and closes the valve 22 in a state in which the system internalpressure is higher than the predetermined pressure α.

The predetermined pressure α may be exerted on the valve 22 in theclosed state from the side of the reserve tank 30 to which the branchpath unit 20 is connected. The above pressure may be detected by apressure sensor, for example. In the present embodiment, the reservetank is a type of tank that is open to the atmosphere. The liquidpressure of the transport medium stored in the reserve tank 30 in theliquid phase is negligibly small as compared with the atmosphericpressure. Thus, in the present embodiment, the predetermined pressure αis the atmospheric pressure. In this regard, the setting of thepredetermined pressure α to the atmospheric pressure includes a casewhere pressure is exerted on the valve 22 in the closed state from theside of the reserve tank 30.

In the present embodiment, specifically, the state in which the systeminternal pressure is higher than the predetermined pressure αcorresponds to an exemplary case where the system internal pressure ishigher than a predetermined pressure β. The predetermined pressure β maybe set higher than the predetermined pressure α. Specifically, the firstcontrol unit may open or close the valve 22 before the operation stopcondition is met (during operation of the internal combustion engine 50)after the operation start condition is met.

Specifically, the suction determination unit acquires the systeminternal pressure and the system internal temperature, and calculates asaturated vapor pressure corresponding to the system internaltemperature. Then, the suction determination unit calculates thedifference between the calculated saturated vapor pressure and theacquired system internal pressure, and determines that air has beensucked when the difference thus calculated is larger than apredetermined value. The system internal pressure may be obtained on thebasis of the output of the pressure sensor 61, and the system internaltemperature may be obtained on the basis of the output of thetemperature sensor 62. The system internal pressure and the systeminternal temperature may be obtained by estimation, for example.

The heat transport device 1A thus structured transports heat so that thetransport medium circulates naturally while the sequence of receivingheat in the condensed state in the heat recovery unit 11 and radiatingheat in the vaporized state in the condensation unit 12 is repeatedlycarried out. Thus, heat is recovered and utilized.

Next, a description is given of an exemplary control operation of theECU 40A with reference to a flowchart of FIG. 2. The present flow may beperformed during operation of the internal combustion engine 50, forexample. The present flow may be performed while the internal combustionengine 50 is stopped. The ECU 40A acquires the system internal pressureand the system internal temperature (step S1). Next, the ECU 40Acalculates the saturated vapor pressure corresponding to the acquiredsystem internal temperature (step S2). Then, the ECU 40A calculates thedifference between the calculated saturated vapor pressure and theacquired system internal pressure (step S3), and determines whether themagnitude of the difference thus calculated is larger than apredetermined value (step S4). If a negative determination is made, theflowchart is once ended.

If an affirmative determination is made in step S4, the ECU 40A acquiresthe system internal pressure (step S5), and determines whether theacquired system internal pressure is higher than the predeterminedpressure 3 (step S6). In this regard, the system internal pressure risesas the heat reception of the transport medium in the heat recovery unit11 progresses, and exceeds the predetermined pressure α and further thepredetermined pressure β. Thus, in step S6, an affirmative determinationis made at the timing of performance of the present flowchart, whichtiming may be a timing after the internal combustion engine 50 isstarted under cold conditions, a timing after a certain period of timepasses and then the internal combustion engine 50 is stopped, or atiming before a certain period of time passes.

If a negative determination is made in step S6, the ECU 40A returns tostep S5. In contrast, if an affirmative determination is made in stepS6, it is determined that the circulation path unit 10 has sucked air.Thus, in this case, the ECU 40A opens and closes the valve 22 (step S7).For example, the valve 22 may be opened until the system internalpressure becomes lower than the given pressure higher than thepredetermined pressure α. As another way, the period of opening thevalve 22 and the degree thereof may be predetermined on the basis of thedifferential pressure between the predetermined pressures α and β. Afterstep S7, the flowchart is once ended.

A description is now given of functions and effects of the heattransport device 1A. When it is recognized that an increase in thesystem internal pressure occurs under the same operating conditions, thevalve 22 is opened and closed with the system internal pressure beinghigher than the predetermined pressure α. Thus, air is expelled from thecirculation path unit 10 together with vapor while the condensedtransport medium remains in the circulation path unit 10, whereby thedevice performance can be recovered in terms of the performance oftransporting heat.

In this regard, after air is expelled from the circulation path unit 10together with vapor, the amount of the transport medium in thecirculation path unit 10 decreases. The system internal pressuredecreases as the cooling of the circulation path unit 10 progressesafter the operation stop condition is met, for example. When the systeminternal pressure becomes lower than the atmospheric pressure, itbecomes possible to replenish the circulation path unit 10 with thetransport medium.

Therefore, the performance of the heat transport device 1A may berecovered in terms of the transport amount by the time when the nextoperation start condition is met after the operation stop condition ismet. The heat transport device 1A capable of recovering the deviceperformance that deteriorates due to the air suction may have astructure that has an advantage in terms of cost because the vacuum pumpis no longer needed, for example. The omission of the vacuum pump isadvantageous in terms of downsizing the structure.

Specifically, the heat transport device 1A opens and closes the valve 22in the state in which the system internal pressure is higher than thepredetermined pressure α, when determining that the circulation pathunit 10 has sucked air. In this regard, the heat transport device 1A maybe configured so that only the system internal pressure is used todetermine whether the circulation path unit 10 has sucked air instead ofboth the system internal pressure and the system internal temperature.

However, in terms of the detection accuracy in this case, it isrealistic to understand a standard system internal pressure forcomparison when the operating conditions are stabilized (for example,when a certain period has elapsed after the internal combustion engine50 is stopped). Therefore, the occasion for detecting the air suctionmay be limited.

In contrast, the heat transport device 1A acquires the system internalpressure and the system internal temperature, and calculates thesaturated vapor pressure corresponding to the system internaltemperature. The heat transport device 1A calculates the differencebetween the calculated saturated vapor pressure and the acquired systeminternal pressure, and determines that the circulation path unit 10 hassucked air when the difference thus calculated is larger than thepredetermined value. Therefore, the heat transport device 1A is capableof detecting the air suction regardless of the operating state of theheat transport device 1A. As a result, it is additionally possible toquickly detect the suction of air.

In the heat transport, the heat transport device 1A transports heat sothat the transport medium circulates naturally while the sequence ofreceiving heat in the condensed state in the heat recovery unit 11 andradiating heat in the vaporized state in the condensation unit 12 isrepeatedly carried out. The heat transport device 1A thus configured iscapable of preventing the vapor from moving diffusely due to the airsuction. Thus, the heat transport device 1A thus configured has apossibility that the heat transport performance deteriorates greatly dueto the air suction and the device performance thus deteriorates greatly.Thus, particularly, the heat transport device 1A thus configured iscapable of suitably recovering the device performance.

In a vehicle with the internal combustion engine 50, the mounting of theheat transport device 1A makes it possible to recover and utilize theexhaust heat of the internal combustion engine 50. The vehicle has alimited space for mounting the heat transport device 1A. In the vehicle,an attempt to hermetically seal the circulation path unit 10 completelyis not realistic when the possibility of the occurrence of agedeterioration and cost are considered. Thus, the heat transport device1A is suitable particularly for the case where the heat transport device1A is mounted in the vehicle with the internal combustion engine 50 andthe heat recovery unit 11 recovers the exhaust heat of the internalcombustion engine 50. In this case, the recovery of the heat transportperformance improves fuel efficiency due to improvements in the warm-upperformance of the internal combustion engine 50.

The heat transport device 1A is provided with the reserve tank 30 towhich the branch path unit 20 is connected. With this structure, thereis no need to further provide a branch path unit for connecting thecirculation path unit 10 and the reserve tank 30 together. The heattransport device 1A thus configured is advantageous in terms of cost anddownsizing.

The connection destination of the branch path unit 20 may be theatmosphere. Even in this case, the device performance may be recoveredby further providing a branch path unit similar to the branch path unit20 and connecting the branch path unit to the reserve tank 30. In thiscase, the branch path unit 20 may be a first branch path unit, and thebranch path unit configured to have the reserve tank 30 as theconnection destination may be a second branch unit.

In the heat transport device 1A, the quantity of the transport mediumwith which the circulation path unit 10 is to be replenished may becalculated timely, and the replenishment with the transport medium maybe performed timely. The heat transport device 1A may be provided with areplenishment quantity calculation unit and a second control unit, whichwill be described later in association with a third embodiment, in orderto calculate the replenishment quantity and perform the replenishmentwith the transport medium. This may be applied to a heat transportdevice 1B, which will be described next.

Second Embodiment

Heat transport device 1B of the present embodiment is substantially thesame as the heat transport device 1A except that the heat transportdevice 1B is equipped with an ECU 40B instead of the ECU 40A. Therefore,the heat transport device 1B is omitted for convenience of illustration.

In the determination of whether the circulation path unit 10 has suckedair in the ECU 40B, the suction determination unit makes a determinationas follows. That is, the suction determination unit of the ECU 40Bdetermines that the circulation path unit 10 has sucked air when themagnitude of the difference between the real quantity of change of thesystem internal pressure corresponding to the quantity of heat recoveredby the heat recovery unit 11 and a predicted quantity of change islarger than a predetermined value.

The quantity of heat recovered is the quantity of heat recovered by theheat recovery unit 11 during a predetermined recovery period. Thequantity of heat recovered may be calculated (estimated) on the basis ofthe quantity and temperature of the exhaust output from the internalcombustion engine 50 at that time. The recovery period may be defined asa period until a predetermined time passes after the operation startcondition is met from the operation stop state (in the presentembodiment, after the internal combustion engine 50 is started undercold conditions). Thus, the thermal states of the heat recovery unit 11and the condensation unit 12 out of the operating conditions can bestabilized.

The real quantity of change may be calculated on the basis of the systeminternal pressure at the start of the recovery period and that at theend thereof. The predicted quantity of change may be preset inaccordance with the quantity of heat recovered within a predicted rangeduring the recovery period, for example. The predicted quantity ofchange may be corrected on the basis of the atmospheric temperature whenthe operation start condition is met, for example.

A description is now given of an exemplary control operation of the ECU40B with reference to a flowchart of FIG. 3. The present flowchart maybe started when the internal combustion engine 50 is started under coldconditions, for example. The ECU 40B acquires the system internalpressure (step S11). In step S11, the system internal pressure at thestart of the recovery period is acquired. Next, the ECU 40B starts tocalculate the quantity of heat recovered (step S12), and determineswhether the recovery period has passed (step S13). If a negativedetermination is made, the ECU 40B returns to step S12. If anaffirmative determination is made, the ECU 40B acquires the systeminternal pressure (step S14). In step S14, the system internal pressureat the end of the recovery period is acquired.

Then, the ECU 40B calculates the real quantity of change in the systeminternal pressure on the basis of the system internal pressure at thestart of the recovery period and that at the end thereof (step S15).Subsequently, the ECU 40B acquires the predicted quantity of changecorresponding to the calculated quantity of heat recovered (step S16).Then, the ECU 40B calculates the difference between the real quantity ofchange and the predicted quantity of change (step S17), and determineswhether the magnitude of the difference is larger than the predeterminedvalue (step S18). If an affirmative determination is made, the ECU 40Bopens and closes the valve 22 (step S19), and ends the flowchart. If anegative determination is made in step S18, the flowchart is ended.

A description is now given of functions and effects of the heattransport device 1B. In the aforementioned heat transport device 1A, airsuction can be detected even when the thermal states of the heatrecovery unit 11 and the condensation unit 12 change transiently.However, the detection accuracy may be degraded more greatly as thechange is quicker. Further, in the heat transport device 1A, the systeminternal temperature may be estimated on the basis of the temperature ofthe cooling water of the internal combustion engine 50. However, in thiscase, there are some cases where the system internal temperature and thetemperature of the cooling water do not have a high correlation betweenthe system internal temperature and the temperature of the cooling waterunder a certain operating condition of the internal combustion engine50. Thus, in such a case, the detection accuracy may be degraded.

In contrast, the heat transport device 1B determines that thecirculation path unit 10 has sucked air when the magnitude of thedifference between the real quantity of change in the system internalpressure corresponding to the quantity of heat recovered in the heatrecovery unit 11 and the predicted quantity of change is larger than thepredetermined value. Thus, the heat transport device 1A is capable ofdetecting the air suction in a situation having a difficulty indetecting the air suction with a high accuracy. In this regard, the heattransport device 1B is capable of suitably increasing the detectionaccuracy by providing it with the suction determination unit previouslydescribed in the first embodiment. In this case, the aforementionedsuction determination unit of the first embodiment may be a firstsuction determination unit, and the suction determination unit may be asecond suction determination unit.

Third Embodiment

A heat transport device 1C of the present embodiment is substantiallythe same as the heat transport device 1A except that the heat transportdevice 1C is provided with an ECU 40C instead of the ECU 40A. The ECU40C is substantially the same as the ECU 40A except the following.Therefore, the heat transport device 1C is omitted for convenience ofillustration. A similar change may be applied to the heat transportdevice 1B.

In the ECU 40C, an replenishment quantity calculation unit and a secondcontrol unit are further implemented. The replenishment quantitycalculation unit calculates the quantity of transport medium with whichthe circulation path unit 10 should be replenished from the reserve tank30. The second control unit opens and closes the valve 22 in accordancewith the quantity of transport medium for replenishment calculated bythe replenishment quantity in a state in which the system internalpressure is lower than the predetermined pressure α after the firstcontrol unit opens and closes the valve 22. In the present embodiment,specifically, the state in which the system internal pressure is lowerthan the predetermined pressure α is a case where the system internalpressure is lower than a predetermined pressure γ. The predeterminedpressure γ is lower than the predetermined pressure α.

The replenishment quantity calculation unit calculates the quantity oftransport medium for replenishment that corresponds to the quantity oftransport medium discharged when the first control unit opens and closesthe valve 22 specifically in the case where the first control unit opensand closes the valve 22 before the operation stop condition is met afterthe operation start condition is met (in the embodiment, while theinternal combustion engine 50 is operating). Specifically, the quantityof transport medium for replenishment may be calculated between thedifferential pressure between the system internal pressure and thepredetermined pressure α and the opening period defined by opening andclosing the valve 22 by the first control unit (in the presentembodiment, further, in accordance with the degree of opening).

Specifically, the second control unit opens and closes the valve 22 inaccordance with the quantity of transport medium for replenishmentcalculated by the replenishment quantity calculation unit in the statein which the system internal pressure is lower than the predeterminedpressure α before the operation stop condition is met after the firstcontrol unit opens and closes the valve 22 before the above operationstop condition is met after the operation start condition is met.

A description is now given of an exemplary control operation of the ECU40C with reference to a flowchart of FIG. 4. When the flowchart of FIG.2 is carried out while the internal combustion engine 50 is operating,the flowchart of FIG. 4 may be carried out subsequent to step S6 duringoperation of the internal combustion engine 50. The ECU 40C calculatesthe replenishment quantity (step S21). Next, the ECU 40C acquires thesystem internal pressure (step S22), and determines whether the acquiredsystem internal pressure is lower than the predetermined pressure γ(step S23). If a negative determination is made, the ECU 40C returns tostep S22. If an affirmative determination is made, the ECU 40C opens andcloses the valve 22 in accordance with the replenishment quantity (stepS24). After step S24, the flowchart is ended.

A description is now of functions and effects of the heat transportdevice 1C. The heat transport device 1C calculates the replenishmentquantity, and opens and closes the valve in accordance with thecalculated replenishment quantity in the state in which the systeminternal pressure becomes lower than the predetermined pressure α afterthe first control unit opens and closes the valve 22. It is thuspossible to recover the device performance in terms of the amount ofheat transported. That is, after air is expelled from the circulationpath unit 10 together with the vapor, the device performance can berecovered in terms of the amount of heat transported as described above.

After the first control unit opens and closes the valve 22, the air thatraises the system internal pressure is expelled and the quantity oftransport medium in the circulation path unit 10 decreases. Thus, inthis case, even before the operation stop condition is met, the systeminternal pressure may become lower than the predetermined pressure αunder a certain heat reception condition in the heat recovery unit 11and a certain heat radiation condition in the condensation unit 12.

In this regard, specifically, the first control unit opens and closesthe valve 22 before the operation stop condition is met after theoperation start condition is met, and then, the heat transport device 1Ccalculates the replenishment quantity in accordance with the quantity oftransport medium that is discharged while the valve 22 is continuouslyopen by the first control unit. Further, the heat transport device 1Copens and closes the valve 22 in accordance with the replenishmentquantity calculated in the state in which the system internal pressureis lower than the predetermined pressure α until the operation stopcondition is met. Thus, the heat transport device 1C is capable ofquickly recovering the device performance in terms of the heat receptionamount without waiting for the progress of cooling the circulation pathunit 10 after the operation stop condition is met.

Fourth Embodiment

A heat transport device 1D of the present embodiment is substantiallythe same as the heat transport device 1C except that the heat transportdevice 1D is provided with an ECU 40D. The ECU 40D is substantially thesame as the ECU 40A except the following. Therefore, the heat transportdevice 1D is omitted for convenience of illustration. In the ECU 40D, areplenishment quantity calculation unit and a second control unit areimplemented as follows.

That is, in the ECU 40D, specifically, the replenishment quantitycalculation unit calculates a residual quantity of transport medium thatremains in the circulation path unit 10 and the quantity of transportmedium that is needed in the circulation path unit 10 when the operationstart condition is met from the operation stop state. Specifically, thesecond control unit opens and closes the valve 22 in accordance with thereplenishment quantity calculated by the replenishment quantitycalculation unit in the state in which the system internal pressure islower than the predetermined pressure α after the operation stopcondition is met.

Specifically, the residual quantity of transport medium may becalculated. That is, the first step is to calculate an integrateddischarged quantity of transport medium that is discharged from thecirculation path unit 10 when the valve 22 opens and closes, and anintegrated replenishment quantity of transport medium with which thecirculation path unit 10 is replenished when the valve 22 is opened andclosed. Then, the residual quantity may be calculated by subtracting theintegrated discharged quantity from the quantity of transport mediumthat is beforehand input in the circulation path unit 10, and adding theintegrated replenishment quantity to the resultant quantity of transportmedium. It is possible to preset the quantity of transport medium thatis needed in the circulation path unit 10 when the operation startcondition is met from the operation stop state.

A control operation of the ECU 40D may be performed by starting acontrol operation similar to the flowchart depicted in FIG. 4 subsequentto step S6 after the internal combustion engine 50 is stopped in a casewhere the flowchart of FIG. 2 is performed while the internal combustionengine 50 is working, for example. Thus, a flowchart that describes thecontrol operation of the ECU 40D is omitted for convenience ofillustration. In the calculation of the replenishment quantity, theresidual quantity may be timely calculated independently of theflowchart of FIG. 4. In this regard, the residual quantity is notlimited to the time when the operation stop condition is met but may becalculated timely together with the residual quantity, for example.

A description is now given of functions and effects of the heattransport device 1D. The heat transport device 1D calculates thereplenishment quantity as described above. The valve 22 is opened andclosed in accordance with the calculated replenishment quantity asdescribed above. It is thus possible to ensure an appropriate quantityof transport medium in the circulation path unit 10 after the operationstop condition is met in order to make ready for the next time when theoperation start condition is met from the operation stop state. Thedevice performance can be recovered as described above in terms of thetransport amount.

Fifth Embodiment

A heat transport device 1E of the present embodiment is substantiallythe same as the heat transport device 1A except that the heat transportdevice 1E is provided with an ECU 40E instead of the ECU 40A. The ECU40E is substantially the same as the ECU 40A except the following.Therefore, the heat transport device 1E is omitted for convenience ofillustration. A similar change may be applied to any of the heattransport devices 1B, 1C and 1D.

The ECU 40E further implements a freezing determination unit and areduction-in-quantity correction unit. The freezing determination unitdetermines whether the transport medium that circulates through thecirculation path unit 10 has a possibility of freezing. If the freezingdetermination unit determines whether the transport medium thatcirculates through the circulation path unit 10 has a possibility offreezing, the reduction-in-quantity correction unit corrects thequantity of transport medium needed in the circulation path unit 10 byreducing the same when the operation start condition is met from theoperation stop state.

For example, the freezing determination unit is capable of determining,on the basis of the atmospheric temperature, whether the transportmedium has a possibility of freezing. In this case, the freezingdetermination unit always detects or estimates the atmospherictemperature and determines that the transport medium has a possibilityof freezing when the atmospheric temperature is lower than apredetermined temperature. The predetermined temperature may be equal toor higher than a temperature at which the transport medium in thecirculation path unit 10 is frozen. The freezing determination unit maybe configured not to always detect or estimate the atmospherictemperature. The freezing determination unit may be configured to haveanother appropriate method for determining whether the transport mediumhas a possibility of freezing.

Specifically, the reduction-in-quantity correction unit corrects thereplenishment quantity by reducing the same. This makes a correction toreduce the quantity of transport medium needed in the circulation pathunit 10 when the operation start condition is met from the operationstop state. The reduction in quantity for correction used at the time ofreducing the quantity for correction may be preset. For example, thereduction-in-quantity correction unit may stop making a correction toreduce the quantity of transport medium when the freezing determinationunit determines that there is no longer any possibility of freezing ofthe transport medium during a given period of time.

A description is now given of an exemplary control operation of the ECU40E with reference to a flowchart of FIG. 5. The present flowchartindicates an exemplary case where the atmospheric temperature is alwaysdetected. The ECU 40E detects the atmospheric temperature (step S31),and determines whether the detected atmospheric temperature is lowerthan the predetermined temperature (step S32). If an affirmativedetermination is made, it is determined that the transport medium has apossibility of freezing. Thus, the ECU 40E reduces the replenishmentquantity for correction (step S33).

In contrast, if a negative determination is made in step S32, it isdetermined that the transport medium does not have the possibility offreezing. In this case, the ECU 40E determines whether a determinationof a zero possibility of freezing is always made for a predeterminedperiod of time (the negative determination is continuously made in stepS32 for the predetermined period of time) (step S34). If an affirmativedetermination is made, the ECU 40E stops reducing the replenishmentquantity for correction (step S35). After step S33, the negativedetermination in step S34 or step S35, the present flowchart is onceended.

A description is now given of functions and effects of the heattransport device 1E. As described above, the heat transport device 1Edetermines whether the transport medium has a possibility of freezingand reduces the quantity for correction when it is determined that thetransport medium has a possibility of freezing. It is thus possible toreduce the amount of heat that the transport medium receives in thecirculation path unit 10 when the operation start condition is met fromthe operation stop state. As a result, it is possible to improve theoperability from the low-temperature conditions.

The heat transport device 1E reduces the quantity of transport medium inthe circulation path unit 10 in accordance with the reduction inquantity for correction, and is thus capable of preventing orsuppressing freezing of the transport medium in the heat recovery unit11 and outside of the periphery of the heat recovery unit 11. This makesit possible to prevent path blocking by freezing and to quickly changethe frozen transport medium to the liquid phase, whereby the operabilityfrom the low-temperature conditions can be improved. Thus, the heattransport device 1E is capable of further improving the operability fromthe low-temperature conditions in recovery of the heat transportperformance in terms of the transport amount.

Sixth Embodiment

A heat transport device 1F of the present embodiment is substantiallythe same as the heat transport device 1E except that the heat transportdevice 1F is provided with an ECU 40F instead of the ECU 40E. The ECU40F is substantially the same as the ECU 40A except the following.Therefore, the heat transport device 1E is omitted for convenience ofillustration.

The ECU 40F further implements a third control unit. The third controlunit opens and closes the valve 22 in a state in which the systeminternal pressure in the circulation path unit 10 does not exceed apredetermined pressure δ after the operation start condition is met. Thepredetermined pressure δ is a pressure that the system internal pressureshould reach.

In this regard, specifically, the predetermined pressure δ may be apressure that the system internal pressure should reach within apredetermined period of time after the operation start condition is met.In this case, the third control unit opens and closes the valves 22 whenthe system internal pressure is lower than the predetermined pressure δwhen the predetermined period of time passes after the operation startcondition is met, for example. The third control unit may open and closethe valve 22 in accordance with the differential pressure between thesystem internal pressure available when the predetermined time passesand the predetermined pressure δ. Instead of the system internalpressure and the predetermined pressure δ, it is possible to use theamount of variation in the system internal pressure and the amount ofvariation when the system internal pressure changes to the pressure thatthe system internal pressure should reach.

A description is now of an exemplary control operation of the ECU 40Fwith reference to a flowchart of FIG. 6. The present flowchart may beapplied to cold starting of the internal combustion engine 50. The ECU40F determines whether the predetermined time has passed after theinternal combustion engine is started (step S41). If a negativedetermination is made, the ECU 40F acquires the system internal pressure(step S42), and determines whether the acquired system internal pressureis lower than the predetermined pressure δ (step S43). If a negativedetermination is made, the ECU 40F ends the flowchart. If an affirmativedetermination is made, the ECU 40F opens and closes the valve 22 (stepS44). After step S44, the ECU 40F ends the flowchart.

A description is now given of functions and effects of the heattransport device 1F. In the heat transport device 1F, when the quantityis decreased for correction, the quantity of transport medium in thecirculation path unit 10 decreases. Thus, the quantity of transportmedium may be short in view of the thermal conditions of the heatrecovery unit 11 and the condensation unit 12 when some time passesafter the operation start condition is met. Thus, the heat transportperformance may be given insufficiently in terms of the transportamount.

In this case, the quantity of transport medium in the circulation pathunit 10 decreases, and the system internal pressure decreasesaccordingly. With the above in mind, the heat transport device 1F opensand closes the valve 22 as described above to increase the amount oftransport medium in the circulation path unit 10. It is thus possible toappropriately improve the heat transport performance that deterioratesbecause of the reduction in quantity for correction.

The quantity of transport medium of heat needed in the circulation pathunit 10 when the operation start condition is met from the operationstop state may be increased after the operation start condition is metin terms of improvement in the operability. In this case, the quantityof transport medium may be preset to a reduced value as compared withthe case with an increased quantity. A similar change may be applied toany of the heat transport devices 1A, 1B, 1C and 1D.

In this case, for example, the valve 22 is opened and closed in a statein which the system internal pressure is higher than the predeterminedpressure α after the operation stop condition is met, whereby thequantity of transport medium in the circulation path unit 10 can bereduced again. This may be applied to the heat transport device 1F thatincreases the quantity of transport medium in the circulation path unit10 if the correction directed to decreasing the quantity is notterminated.

Although some embodiments of the present invention have been described,the present invention is not limited to these embodiments, but variousvariations and changes may be made within the scope of the claimedinvention.

For example, in the above-described embodiments, a description is givenof the transport medium that is H₂O. However, the present invention isnot limited to this, but an appropriate transport medium such as alcoholmay be used. There is no need to put the transport medium into thecirculation path unit under a depressed condition. Even in this case,cooling progresses when the operation stops, and the condensation of thetransport medium progresses, whereby the inside of the circulation pathunit is brought into the vacuum state and suction of air takes place.For example, the heat transport device may be a heat transport mediumwith a Rankine cycle.

DESCRIPTION OF REFERENCE NUMERALS

Heat transport device 1A, 1B, 1C, 1D, 1E, 1F Circulation path unit 10Heat recovery unit 11 Condensation unit 12 Branch path unit 20 Valve 22ECU 40A, 40B, 40C, 40D, 40E, 40F

1. A heat transport device comprising: a circulation path unit in whicha heat recovery unit that vaporizing a heat transport medium and acondensation unit that condenses the heat transport medium vaporized inthe heat recovery unit are incorporated, and which has a vacuum state; abranch path unit which branches from the circulation path unit, and inwhich a valve capable of controlling flow is incorporated; and a firstcontrol unit configured to open and close the valve in a state in whichpressure in the circulation path unit is higher than a predeterminedpressure when it is detected or estimated that the circulation path unitsucks air, wherein: the heat transport device further comprises areserve tank that stores, in a liquid phase, heat transport medium withwhich the circulation path unit is to be replenished, the branch pathunit being connected to the reserve tank so as to have an openinglocated in a position lower than a height of a liquid level that is tobe at least ensured in the serve tank; and wherein the heat transportdevice further comprises a replenishment quantity calculation unit thatcalculates a quantity of heat transport medium with which thecirculation path unit should be replenished from the reserve tank, and asecond control unit configured to open and close the valve in accordancewith the quantity of heat transport medium calculated by thereplenishment quantity calculation unit in a state in which the pressurein the circulation path unit is lower than the predetermined pressureafter the first control unit opens and closes the valve.
 2. (canceled)3. The heat transport device according to claim 1, further comprising: afreezing determination unit that determines whether the heat transportmedium circulating in the circulation path unit has a possibility offreezing; and a reduction-in-quantity correction unit that performs areduction-in-quantity correction in which the quantity of heat transportmedium is reduced when an operation start condition is met from anoperation stop state if the freezing determination unit determines thatthe heat transport medium that circulates in the circulation path unithas a possibility of freezing.
 4. The heat transport device according toclaim 1, wherein the heat transport medium naturally circulates in thecirculation path unit while a sequence of receiving heat in a condensedstate in the heat recovery unit and radiating heat in a vaporized statein the condensation unit is repeatedly carried out.
 5. The heattransport device according to claim 1, wherein the heat transport unitis mounted in a vehicle with an internal combustion engine, and the heatrecovery unit recovers exhaust heat of the internal combustion engine.